I want to get host name from and inner URL. how to take that.
eg :- this is the inner url format .. http://hostname.com/folder/folder2/test.php?id=243432432424
Use parse_url.
You want the 'scheme' and 'host' elements of the output array (and maybe 'port', 'user' and 'password' as well - you can use http_build_url to stick these bits together if you want).
A concise way would be:
$url = 'http://hostname.com/folder/folder2/test.php?id=243432432424243';
echo parse_url($url, PHP_URL_SCHEME).'://'.parse_url($url, PHP_URL_HOST);
This produces:
http://hostname.com